clean "SLACK SPACE" or TIPS OF THE CLUSTERS

In addition to free disk space there is "slack space" associated with each file and which is completely separate from the ordinary free space.

WHAT IS SLACK SPACE OR TIPS OF CLUSTERS

Disk space is allocated in "clusters", and each cluster can be as large as 65,536 bytes.This means that a file of only 1 byte in size can use 65kb of disk space.This additional, unused space allocated to a file is called the "slack space"

and can contain old, and possibly valuable data which needs to be cleaned.

Cleaning Slack space would (in any conventional way of cleaning it) entail moving every file on your hard drive, which could not be doe for all items while your system is running, and to do it right would require a boot-disk. This is not a practical request for this type of utility.